Machine-switching telephone-exchange system



Dec. 21 1926. 1,611,692

R. L. STOKELY MACHINE SWITCHING TELEPHONE EXCHANGE SYSTEM File p 1920 10Sheets-Sheet 1 Busy fest Dec. 21 1926.

R. L; STOKELY- MACHINE SWITCHING TELEPHONE EXCHANGE SYSTEM Filed Sept.25, 1920 10 s t 1-, 5

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R. L. STOKELY MACHINE SWITCHINGl TELEPHONE EXCHANGE SYSTEM Filed Sept.25. 1920- 1Q sheets-Sheet G //4v V6/4/0l: Hay A. Sfake/y Dec. 21,1926.1,611,692

R. L. STQKELY MACHINE SWITCHING TELEPHONE EXCHANGE SYSTEM 7 Filed Sept.25. 1920 1Q s t s t 7 CHE Om /n van for: Ray L. SMA e/y Dec. 21 1926. 31,611,692

, R. STOKELY MACHINE SWITCHiNG TELEPHONE EXCHANGE SYSTEM Filed Sept.25.1920 10 s s she 't 8 #5 "S W a H 2% o o s Q o 0 Q Q ls k &

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Dec. 21 1926.

' R. L. STOKELY MACHINE SWITCHING TELEPHONE EXCHANGE SYSTEM Filed Sept.25. 1920 1Q h sy h g 9 Aw Q Dec. 21 1926. -1,611,692

R.' L; STOKELY MACHINE SWITCHING TELEPHONE EXCHANGE SYSTEM Filed Sept1920 10 Sheets-Sheet l0 Patented Dec. 21 1925.

UNITE STATES RAY L. STOKELY, OF FLORAL PARK, NEW "SIC-BK, ASSIGNOB TOW'ESTER-N ELECTREG'CO,

, 1,611,692 PATENT OFFICE.

INCORPORATED, 61 NEW YORK, Y., ACOEFGRATIONOF NEVT YORK.

MACHINE-SVII'ICHING TELEPI-IGNE-EXGHANGE SYSTEM;

Application filed September 25, 18-20. Serial No. 412,795.

This invention relates to telephone exchange systems employing machineswitch iug equipment and its object to provide an improved circuitarrangement to take care of toll calls in such systems, some or all ofthe substations whereof are equipped with coin boxes.

In accordance with one feature of the invention the toll ope 'ator afterhaving built up a connection to the substation selects the connectingcircuit used by means of an automatic switch. This switch is accessibleto the .toll operator over two paths, the path chosen determining thecharacter ofoperating current to be applied to the line to actuate thecoin disposal magnet in the coin box, which current is automaticallyapplied as soon as the connecting circuit is selected. Morespecifically, a circuit leading to an automatic switch is equipped withtwo jacks, one having a source of positive current associated therewithfor connection to said circuit and the other a source of negativecurrent. After the operator has built up the toll connection, sheinserts the plug in the positive or collect jack, and by means-of herdial sets the automatic switch to select the connecting circuit overwhich she has built up the connection. A circuit change thereupon takesplace to connect the collect cur rent to such circuit and thence to theselected telephone line to operate the magnet in the coin box to collectthe coins deposited by the subscriber. If the coins are to be refunded,the operator inserts the-plug into the refund jack and likewise sets theautomatic switch on multiples of the used trunk. Upon the completion ofthe selecting operation in this case, a circuit change takes place toconnect the refund current to the connecting circuit and thence to theline to operate the coin box magnet to refund the coins. I

Preferably, the selection of the proper current is controlled by adouble wound relay which normally prepares a circuit from the refundsource to the brushes of the.

operators automatic switch, but when the plug is inserted in the collectjack an energizing circuit for the relay is closed to shift theconnections to the collect source.

Referring to the drawings, Fig. 1 shows a toll cord circuit, Fig. 2shows a trunk circuit outgoing from the toll board to a full me chanicalo'l'l'ice, Fig. 3 shows a selector cir cuit, Fig. 3 shows afragn'ientary modificaig. 3, Fig. 4 shows the relay and repeating coilequipment associated withthc toll transmission select-or circuit, Fig. 5shows the toll transmission selector circuit, Fig. 6 shows a combinationtoll and local connector circuit, Fig. 7 shows the combination toll andlocal connector circuit for party line working, Fig. 8 shows a connectorcircuit for P. B. X. working, Fig. 9, shows a so-calledtoll terminalloop connector circuit, Fig. 10, shows the trunk circuit with connectorfor coin collect or refund, F 11 is a diagram of the manner :in whichthe drawings should be placed together in order to read the circuit.

Referring first to Fig. 1, this drawing shows a cord circuit at the tolloperators position. The left hand side of this circuit will be calledthe toll end and the right hand will be called the toll and trunk end.The operator answers an incoming call by insert ing the plug T of thetoll end in the an swering jack J in the ordinary manner. If the calledsubscriber is located in a nearby exchange, the call is completed byinserting the plug T1 of the trunk and toll end in a toll switchingtrunk jack TSJ. Theoperator then actuates the dialing and monitoring keyDK which causes the relay -B34 to operate, which in operating energizesa monitoring relay not shown) to place the operators telephone set in amonitoring po sition on the cord. The operator now turns the dial 1) forthe first digit of the wanted number. The dial in moving out of itsnormal position short circuits the relay E e-l4: permitting the relayE--72 to operate.' Relay E72 in operating locks itself to bat tery andtransfers the tip of the plug TT through the impulse springs of the dialto the battery. The dial, inreturningto nor-' mal, interrupts thebattery connected to the tip of the plug causing the impulse relay ofthe trunk circuit of Fig.2 to operate intermittently, the number oftimes depending upon the digit involved. This impulse re-, lay, in thusoperating, causes the setting of the selector circuit of Fig. 3, whichthereupon. automatically picks out an idle trunk in the selected level.lVhen the operator has operated the dial for all the digits involvedwhich causes the last switch to be set on the desired line, she restoresthe monitoring DK. If the called. line is not busy, thetrunk and llt itoll supervisory lamp 100 l ghts, as a ringing sgnal. whereupon theoperator by depressing ringing key RK causes the connector to start theringing of the called line, which ringing continues until the calledparty answers, whereupon the lamp 100 is extinguished. \Vhen the calledsubscriber replaces his receiver, this lamp again lights.

lit the called line is busy or if one of the selectors had failed tofind an idle trunk, the lamp 100 will flash, the frequency oi? theflashes depending upon the busy condition encountered. The toll operatorin response to the flashing of the lamp removes the plug 'l 'l ot thetrunk and tell end of the cord from the toll switching ack TSJ, butbefore removing the toll plug T the operator by means of her ringing keyRK, rings on the toll line terminating at the jack J to notify thedistant operator that the line is tree. 1f the distant operator ringsfirst, however, the toll supervisory lamp 101 lights and is extinguishedby operating listening key LK or 'pullingoutthe plug T. It the calledsubscriber is a distant one reached over a toll line, the toll operatorinserts the plug TT of the trunk and toll end in the proper jack and by111651118 0)? her ringing key RH. applies alternating current to thetrunk to signal the distant operator. 1V hen the operator at the distantend applies ringing current to the trunk, the toll supervisory lamp 101lights until the listening key Lli operated or the connection is takendown. The keys K and K serve, when operated, to disconnect either end ofthe cord from the operators telephoneset when the operator is talking onthe other. When the plug '1 of the toll end is inserted in a tollanswering jack, relay E-156 operates, in turn operating relay B162.Relay- 13-162 opens the circuit of relay E162 preventing the tollsupervisory lamp 101 from lighting. When the plug TT of the trunk andtoll end is inserted in toll switching trunk jack TSJ, relay F99operates in series with relay 1 1- 155 and the lower winding of relayll156. Belay l l-09 disconnects the busy test equipment of the operatorstelephone set from the tip of the cord and connects the tip of the cordthrough t0 the ringing key. Relay E155 is marginal and does not operateat this time on account of the high resistance in the sleeve of thetrunk circuit; Ringing current applied by the distantoperatorover thetoll line operates the relay A-190 which releases relay B162. The latterrelay in'releasing lights the toll supervisory lamp 101 and operatesrelay E-162 in parallel with the lamp. Relay 1 1 162 locks up under thecontrol of the listening key LK and relay 15-456 so that the lampremains lighted after the ringing ceases and the relay 13-162is'reoperated through the back contact of relay A 190.

relav E--162 operates and locks.

Thelamp 101 may be extinguished by operating the listening key 'hichreleases relay E-l62 or by taking down the connection which releasesrelays l*l15t5 and F-1b2. Relay 13-162 is made slow in operating toguard against the possibility of lamp 101 being lighted by Morseimpulses. Relay A19(5 may be operated for a short time by Morse impulsesbut will not remain operated long enough to cause the operation of relaylE-162. In case'relay l 1(32 should release momentarily, the slowoperating feature of the relay 1') 102 will give the formertime tore-operate before the u W' hen both ends of the cord are inserted in thetoll line jacks the marginal relay E 155 disconnects the relay B--1:-ifrom the cord circuit. When ringing current is received from either ofthe distant oiiices, relay A100 operates and lights the lamp 101. It, ona through toll connection of this character, the splitting key K isoperated to disconnect the trunk and toll end from the operatorstelephone set, relay 15%; is bridged across the trunk and toll end sothat it will operate when ringing current is received from the distantmike and flash the lamp .100. When the splitting key K is in its normalposition the circuit for relay li ecg opened.

Referring now to Fig. 2 which represents a toll switching trunk overwhich a connection is extended to a nearby exchange, relay C-2 operatesover its right hand winding when the operator inserts the plug 'i l intojack TSJ and by attracting its armature closes a loop circuit leading tothe impulse relay A E Fig. 3, of the first selector. which in operatingenergizes slow relay B3 to prepare the impulse circuit. When the dialingkey DK is thrown and the dial is operated, relay A2 operates connectingrelay I2 across the loop leading to the impulse relay A3, Fig. 3. Relayl2 in operat ingcauses relay D-2 to operate, which relay shunts the lefthand winding of relay C2 whereupon the latter relay releases, a circuitthrough its right hand winding being opened whenrelay E72, Fig. 1,operates as the dial is moved out of its normal position. Relay D2 inoperating operates relay El which locks up to the ground at the innerleft'cont-act of relay B 2, now energized. Relay E'2 at its outer lettcontact holds up relay D2, independently oi, its ori "inal energizingcircuit, at the front contact oi rclay 1 2. The dial in restoringintermittently operates relays A 2 and 1 2, relay l2 alternatelv openingand closing a shunt path arounu relay I)-2. If. during the operation ofbuilding up a connection. one of the selectors fails to tind an idletrunk in the selected group. it opens the loop circuit including relayI2. Relay I-2 in closing inn lli'i its back contact, shunts out relayD9.. Re-

lay l)--:l in closing its right hand back cou-.

tact operates relay lli Relay l-l-S locks up and connects interruptedbattery of (it) impulses per minute to the windin of relay C-2 in shuntot' the supervisory relay B- l3 in the cord circuit, Fig. 1. Relayfollows these impulses and flashes the supervisory lamp 100 to indicateto the operator the failure to tind an idle trunk. In case the calledline is idle. this condition causes the polarized relay FL to operatewhen the operator restores the key Dli which, in operating energizesrelay G.3 which cuts the trunk through, thus disconnecting the relay C-2and A2 from the circuit leading back to the toll operators position. Incase the called line is busy, however, this polarized relay does notoperate, the relays A2, I-2 and D-2 remain energized. the relay H2 isnot operated and at its inner back contact connects interrupted batteryof 120 impulses per minute to the winding of relay G-2 which causes thesupervisory lamp 100 to flash to indicate to the operator the busycondition of the selected line. y r

Referring now to Fig. 10. When the op.- erator has built up theconnection and found the line idle, applied ringing current, and thesubscriber who originatedthe call and against whom the call wasoriginally charged has responded, she requests the Slll)SClll')0l' todeposit the required coins in the coin box, which preferably of the typeshown in Patent. No. 1,043,219 of Nov. 5, 19l2,'to O. F. Forsberg. Thecoins, in droppingin the coin box, strike bells which, in the well knownmanner, inform the operator of the character of the deposited coins. Theoperator then picks up a plug P and inserts it in a collect jack J10 ather position, and by means of the dial D1O and an automatic switch shownin Fig. 10, selects the trunk shown in Fig. 3 which is multipled to thisautomatic switch. If the plug is inserted into the collect jack a relayH10 oper' ates to prepare a circuit from a source of current of 110volts positive polarity to the selected line to operate the polarizedmagnet in the coin box to collect the coins. It, on the other hand, theplug P-10 is inserted in the retund jack R1.0, relay H1O is not operatedand consequently negative current of 110 volts is impressed upon thecalled line to operate the polarized magnet in the coin box iii-theopposite direction-to refund the coins. The upper armature ot' the relayll- 10 in its attracted position closes a cir cuit tron! a tone sourceof one character to the operators head set which intorms her thatpositive impulses of current are being transmitted to the called line.This relay in its attracted position gives a different tone to theoperators head set to indicate to her Consequently,

' Having described in a general manner the operation of the system, acall will now be v traced in detail.

The toll operator, having been informed of the number of'the wanted lineand assun'iing this line to be in a. nearby exchange, tests for an idletrunk by touching the tip of her plug TI to the sleeve of the ack TSJ ofthe toll switching trunk in the Well known manner, and it she does notreceive a click in her receiver she inserts the plug TT into the tollswitching trunk jack TSJ. A circuit is thereupon closed to operaterelays E-'99,,

(Fig. 1) and l3-2 (Fig. 2). RelayE-Qt). iuoperating disconnects theoperators busy test circuit from the tip of the-cord. Relay l 2 (Fig. 2)in operating prepares certain circuits which willbe traced later. T histrunk will new test busy at the other operator's positions due tobattery applied to the sleeve multiples by the sleeve of the plug T T.The insertion of the plug also closes the t'ollowing circuit to energizerelay C 2: tree pole of battery, resistance 200, right hand winding ofrelay (3-2, conductor 201, armature 202 of relay G2, conductor 203, ringof the jack TSJ and plug TT, conduct-or 110, lower IlO111'1al CO11t21Ctof ringing key RK, rightliand winding of retardation coil 111, relay'B-l-3, armature and back contact of relay which is not operated whenthe plug TT is inserted in the tol trunk switching jack, but only whenit is inserted in a toll line leading to a distant otlice, left handwinding of retardation coil 111, upper normal contact of ringing key BK,armature andfront contact 'otrelay E99, conductor 102, right hand normalcontact of relay E72, conductor'103, tip of the plug TT, tip of the ackTSJ, arinatin'e 204, back contact of relay G 2, and relay A-2 to ground.Relay A2 is marginal and does not operate in this circuit. Relay C 2 inattracting its armature closes the following circuit to operate relayA3, Fig. 3, which is the impulse relay ot the first selector, which isshown in Fig. 3: free pole of bat-' tery, lower winding 0t relay A.-3(Fig. 3), conductor 300, back contact and armature 301 of relay D'3,conductor 302, conductor 205, conductor 206, outer left hand armatureand back contact of relay ll2, conductor 20?, armature and front contactof relay C2, left hand winding of relay C-2, conductors 208 and 209,inner right armature and front contact of relay B2, conductor 210,polarized relay F 2, conductor 211, conductor 212, conductor 803,armature 304, back contact of relay D3, conductor 305, upper winding ofrelay A-3, conductor 306,

normally closed contact of switch 307, op-

erated on the eleventh rotary step of the selector, to ground. Theoperator now throws the dialing and monitoring key DK, whereupon acircuit is closed to operate relay B34l, Fig. 1, which in attracting itsarmatures causes the operator's head set to be connected across thecord. She now rotates the dial D for the first digit of the wantednumber. The closure of the contact 104 of the dial as the dial moves offnormal, shunts the relay B3 l which operates the relay E-72 and releasesrelay B34. Relay E72 in attracting its left hand armature locks itselfto ground at the contact of the dialing key DK which whenactuatedremains in its operated position until manually released by theoperator. Relay I l-72 in closing its right hand contact con nects thefree pole of battery through the impulse contact 108 of the dial to thetip of the plug interposing a break in the tip conductor. Theinterposition of this bneal: in the tip conductor opens the circuitheretofore traced through the right hand winding of relay C2. Marginalrelay A-2 now operates in series with the impulse contact of the dial,the circuit being as follows: free pole of battery, resistance 109,impulse contact 108, right hand armature and front contact of relay E72,conductor 103, tip of the plug TT, tip of the jack TSJ, armature 20% andback contact of relay G2,

conductor 213 and relay A-2 to ground.

Relay A2 in attracting its left hand armature bridges relay 1-2 acrossthe tip and ring of the cord in parallel with the left hand winding ofrelay C2. Relay I2 in attracting its armature closes a circuit, tooperate relay D2 as follows: free pole of battery, resistance 214conductor 215, relay D2, conductor 216, right armature and front contactof relay I-2 conductor 217, contact 218 of relay G-2 to ground. Relay D2in attracting its left armature short circuits the left hand Winding ofrelay C2 which thereupon releases. thus opening one hand armature andfront contact of relay A-2, conductor 211, conductor 212, conductor 303,armature 30a; and back contact of relay D3, conductor 305 upper windingof relay A3 and upper normal contacts 307 to ground. Relay D-2 at itsright armature and front contact closes the following circuit to operaterelay E 2: free pole of battery, relay E2 conductor 220, right armatureand front contact of relay 1)2, conductor 221, conductors 222 and 228,inner left armature and front contact of relay l-2 to ground. Relay E2in attracting its inner right armature locks itself to groundedconductor 222. The functions of this relay will be later described. DialD, Fig. 1, in returning to normal, interrupts at its impulse contact 108the circuit of the impulse relay A2, Fig. 2, which at its left armatureinterrupts the circuit of the impulse relay A3, Fig. 3, the number oftimes corre' sponding to the first digit of the wanted number. Upon eachretraction of the armature of relay A3, the following circuit is closedfor the vertical magnet 310 of the first selector: grounded armature311, and back contact of relay D3, conductor 312, armature and backcontact of relay A 3, lower armature and front contact of relay B3, slowrelay C-3, vertical magnet 310, and free pole of battery. On the firststep of the selector off normal springs 313 close the following circuitfor relay 31 1-: free pole of battery, relay 314., conductor 315, offnormal springs 313, conductors 316, 31?, armature and front contact ofrelay C3 to ground at the armature and front contact of relay B-3. Relay314 in attracting its upper armature locks itself over the followingcircuit: free pole of battery, relay 314C, conductor 315, off normalcontact 313, conductor 316, armature and back contact of rotary magnet318, conductor 319, conductor 320, upper armature and front contact ofrelay 314i, conductor 321 to ground at the armature 311 and back contactof relay D3. Upon the cessation of the impulses, however, relay A3remains energized and consequently relay C 3 which is slow to release,after an interval, releases whereupon the following circuit is closed toenergize the rotary magnet 313 of the selector to step the selectorbrushes on to the first trunk in the selected level: free pole of.battery, magnet 318, conductor 322, lower armature and front contact ofrelay 314, upper normal contact of relay C3, upper armature and frontcontact of relay B3 to ground. At the end of its stroke, the rotarymagnet 318 opens the locking circuit traced for relay 314. Relay 314; inretracting its lower armature opens the circuit of the rotary magnet. Ifthe first trunk is busy, ground is present on the test multiple 323thereof, whereby the following circuit is closed to energize relay 314:

hill

grounded multiple 823, test brush 324, conductor 325,- armature 326 andback contact of relay D3, conductors 327, 319, back con-- act andarmature of magnet 318, conduct-or 2310, contact 313, conductor 315,relay 31 1 to free pole of battery. Relay 314. in attracting its upperarmature again locks itself through the back contact oi" the rotarymagnet and in attracting its lower armature again closes the circuit ofthe rotary magnetwhereupon the selector brushes are stepped to the nexttrunk. This action of the relay 314C and rotary magnet is continueduntil an idle trunk is found which is indicated by the absence of groundon the test multiple 323 thereof. When the rotary magnet at the end ofits stroke positions the brushes on to an idle trunk and no ground ispresent, relay 314 does not energize but relay DS energizes over thefollowing circuit: iree pole of battery, relay 31a, conductor 315,contact 313, conductor 316, armature and back contact of rotary magnet318, conductor 319, conductor 327, conductor 328, relay 13-3, conductor329, lower normal contact of switch 307, conductor 33 to ground at theupper armature and trout contact of relay B3. Relay 31 is marginal anddoes not operate in this circuit. Relay D3 in attracting its armatures 1and 301 extends the talking conductors through to the selector brushesand cuts of? impulse relay A3.

Assuming now that the selector has failed to find an idle trunk. In thatevent on the eleventh rotary step, switch 30? operates and opens at itsuppermost contacts, the circuit of the impulse relay .+'\3 which causesthe selector (Fig. 3) to restore.

The opening of this loop circuit also causes relay l2 to be permanentlydeenergized. Relay A2 in remaining attracted and the relay I-2 beinginert, the following short circuit is closed about the slow relay l) 2to cause the same to release: free pole oi battery. resistance 214,right hand armature and front contact of relay A-2, armature and backcontact of relay I-2, conductor 217. contact 218, to ground. It will heunderstood that relay D-2 is slow to release as shown and holds upbetween the impulses of one digit. Relay D-2 in re- 1ra- ;-ling itsright armature operates relay I l-2 over the following circuit: freepole of battery. relay H2, conductor 222. armature and. back contact ofrelay D-2, conductor 220, inner right hand armature and trout contact ofrelay E-2 to ground on conductor 24-2. Relay I *2 in attracting itsinner le'tt armature locks itself up to grounded conductor 242 and inattracting its inner right armature connects interrupter to the innerleft hand armature and front contact oi? relay Fi2 to shunt thei'csisuance 200 to cause supervisory relay l3-43 in the cordcircuittoflash the trunk ancltoll supervisory lamp 100 at the rate offlashes per minute when the operator restores the key DK. -This rate offlashing will indicate to'the operator that one of the switches hasencountered a busy trunk group whereupon she will pull out the plug andwill thenwait and set up the connection later, or insert the plug intoanother jack and again set up the connection by way of another trunk.lVhile the interrupting machine 223 is connected to the front contact ofrelay H2 as soon as relay D-2 releases, this operation is not effectiveto flash the lamp until the operator, after having turned the dial forthe last time, releases her dialing key DK, Fig. 1. The opening of helowermost contact of this key releases relay E72 which in retracting itsright armature again closes the loop circuit including the right handwinding of relay 0-2, Fig. 2, and the relay A2 Fig. 2 and B-4E3 (Fig.1). It will, of course, be understood it no idle trunk is found relay G2is not energized.

The relay H2 in attracting its outer left armature interposes a break inthe loop circuit leading'to the selector (Fig. 3) thus presenting thesubsequent sets of impulses from operating the switches.

The seizure of the toll transmission selector, Fig. 5, with which therelay and repeating coileequipment of Fig. l is associated, causes theclosure-0t the following circuit for impulse relay .A5, Fig. 5 of thetoll transmission selector: tree pole of battery,

right hand winding of relay A5, conductor 500, conduct-or 4100,conductor 401, outer left armature --and back. contact of relay B-t,conductor 402. contact 403 of relay F4-, conductors 104, 4:05, upperleft hand winding of repeating coil 406, conductor 407, multipleterminal 351, brush 350, conduct-or 352, armature 304 and front contactof relay D-8, conductors 303, 212, conductor 211, left armature andfront contact of relay A2, relay I2, conductors 298, 207, outer let'thand armature and back contact ot relay I-l2, conductors 206, 205, 302,armature 301 andtront contact of relay D Z). conductor 332,.brush 3333,multiple terminal 334:, conductor 408, lower left hand winding ofrepeating coil400, conductor 409, contact 410 of relay F-4, conductor411, contact 412 of relay B4, conductor 413, conductor 501, through theleft winding of relay A-5 to ground. at the lower normal contact. of theswitch 502. which is operated on the eleventh rotary step of thetransmission selector. The impulse relay A5 in attracting its rightarmature energizes slow relay l" 5. This relay in attracting its leftarmature closes a circuit for relay which in attracting its armaturesapplies a local ground to the test multiple to cause this trunk to testbusy. Relay 336 is provided when the til) transmission selector is notlocated in the same otlice as the selector circuit of Fig. 3, to takecare of differences in ground potentials and trunk resistances. If thetoll selector is in the'same office, ground from the outer left armatureand front contact of relay B5 is transmitted to the test muliple 323,

called line causing relay A2 Fig. 2 to open and close the loop circuitfor the relay A5, which in vibrating its right hand armature transmitsimpulses over the following circuit to the vertical magnet 508 of thetoll transmission selector: right armature and back contact of relay A5,inner armature and front contact of relay B.5, conductor 509, armature510 and back contact of relay D5, conductor 511, slow relay C--5, magnet508. to free pole of bat-- tery. The brushes of the toll transinisslonselector are thus elevated to the desired level. When the dial returnsto normal and maintains the relay A-2 energized, relay A.5 remainsenergized and, after a slight interval, slow relay C5 releases. When therelay -5 operated on the first impulse and the selector took its firststep, relay E-5 corresponding to relay 314, Fig. 3, operated over thefollowing circuit: free pole of battery, relay E-5 upper contact of offnormal switch 515, conductor 516, armature and front contact of relayC-5, conductor 517, conductor 518, conductor 503 to ground at the rightarmature and front contact of relay 13-5. In attracting its innerarmature, relay E5 locks itself to the upper armature and back contactof slow relay F5, this circuit including the armature and back contactof rotary magnet 519. These circuits are similar to those of theselector of Fig. 3. Upon the cessation of. the impulses and thereleaseof the slow relay C5, the circuit of the rotary magnet is closed asfollows: free pole of battery, magnet 519, outer armature and frontcontact of relay E5, normal contact of relay (3-5, conductor 517,conductor 518, conductor 503, right armature and front contact of slowrelay l3 5 to ground. The rotary magnet advances the brushes on to theterminals of the first trunk and at the end of its stroke opens thelocking circuit of the relay E5 which releases opening the circuit ofthe rotary magnet. If the trunk is busy, relay E5 again energizes overthe following circuit: free pole of battery, relay a-5, upper contact ofswitch 515, conductor516, conductor 520, armature and back contact ofrotary magnet 519, conductor 521, conductor 522, back contact andarmature 523 of relay D-5, conductor 524, lowermost armature and backcontact of relay F5, conductor 525, test brush 526 to ground on the testmultiple 527. Relay .F-5, in attracting its inner armature again locksup through the upper armature and back contact of relay F 5 and at theother armature again closes the circuit of the rotary magnet whichadvances the brushes to the next trunk and at the end of its strokeopens the locking circuit of relay E 5 which in retracting its armatureopens the circuit of the rotary magnet 519. The switch 502 of the tolltransmission selector, Fig. 5, corresponds to the switch 307 of theselector circuit, Fig. 3. Its function is to open the circuit of theimpulse relay A-5 on the eleventh rotary step of the toll transmissionselector, that is to say, if all the trunks in the group are busy. Theopening of this circuit releases the switch and causes relay 1-'2, Fig.2, to become permanently inert which causes the release of slow relay 2and prepares a circuit for the interrupter 2 3 which results in theflashing of the trunk and toll supervisory lamp 100 when the operatorrestores her dialing key as described in detail in connection with Fig.3. If, however, an idle trunk is found, relay D5, which corresponds torelay l)3, Fig. 3, ope ates over the following circuit: free pole ofbattery, relay E5, upper contact of switch 515, conductor 51G, conductor520, armature and back contact of magnet 519, conductors 521, 522, relayD5, upper normal contact of switch 502, conductors 530, 503 to ground atthe right armature and front contact of relay 502. Relay E5 is marginaland does not operate in this circuit in series with the relay D5. RelayD5 then operates and in attracting its armatures 531 and 532 extends thetalking conductors through to the talking brushes 533 and 534. Theattraction of the armature 523 of relay D5 grounds the test brush 525and consequently test multiple-527 of the selected trunk, causing thesame to test busy to other selectors. The contact 535 is made before thecontact 500 is broken by the armature 537 of the relay D5. Consequentlyrelay D4, Fig. 4. in the relay and repeating coil equipment ismaintained energized over the following circuit: free pole of battery,relay D4 conductor 415, outer right armature and back contact of relayF-4, conductor 414, conductor contact 535, conductor 538,

cuit. Relay D& in retracting its outer right hand armature operatesrelay F 4, Fig. 4, over thefollowlng circult: free pole of battery,relay F4, conductor 428, outer right armature and back contact of relayD4, conductor 429, conductor 550, armature and front contact of relayD5, conductor 518 to ground at the right armature and front contact ofrelay B5. Relay F4 in attracting its outer right armature closes asubstitute ground to hold up the relay F6 to prevent ringing fromoccurring at this time: ground right hand armature of relay El,conductor 430, right armature and back contact of relay l:$4, outerright armature and front contact of relay 1 -4, control conductors 4:14and 501', contact 535 of relay D5, conductor 538, brush 539, multiple540, conductor 541, conductor 600, front contact, armature 685 and lowerwinding of relay F6 to free pole of battery. Relay I -6 was energizedupon the first impulse .to the vertical magnet, this circuit being asfollows: free pole of battery, lower winding of relay F6, lower armatureand front contact of slow relay 619, innermost righthand armature andfront contact of relay J-6, conductor 614, conductors 631 and 615 toground at the upper inner armature and front contact of relay B6. Whenenergized, relay F-6 locks by Way of its armature 635 and front contact,conductor 601, armature 602 and back contact of relay K-6 to groundedsleevewire 650. Consequently, the operation of relay K-6 to cause thereversal of direction of the current flow in the loop leading back tothe toll operators position would deenergize relay F-6, and unless asubstitute circuit is provided for holding up relay F--6 the ringingoperation would automatically take place. This is prevented by applyingground to the control conductor 600 over the circuit traced to hold therelay F -6 until the operator, by depressing a key as will be explained,releases relay F-6 to start the automatic ringingoperation. The releaseof the relay D1 and the consequent energization of relay F-4 asdescribed reverses the direction of current flow in the talkingconductors lead- 1ngback to the operators position. After having turnedthe dial for the last time, the operator restores her dialing key DKwhich releases relay E-72 which disconnects the dial from the tip of theplug-causing the release of the relay A-2, Fig. 2, and causes theclosure of an energizing circuit for the right hand winding of relay -2,relay B-lS and relay A2. Relay A2 it will be remembered, releases underthis condition and in retracting its left armature deenergizes relayI-2, which in releasing causes the release of relay D-2. The polarizedrelay F2 is now bridged across the following circuit: upper talkingconductor 212, l ig. 2, conductor 211, polarized relay F-2, conductor210, inner right armature and front contact of relay B2, conductor 209,conducior 208, left hand winding of relay 0-2, armature and frontcontact of relay C2, conductor 207, outer left armature and back contactof relay H2, conductor 206 to lower talking conductor 205. The reversalof the direction of current in these talking conductors due to theoperation of relay F-4 causes the relay F2 to cooperate closing thefollowing circuit for relay (Jr2:'free pole of battery, relay G2,conductor 22%, contact 225, of relay F2, conductors 226, 227, 228, innerleft armature and front contact of relay 13-2 to ground. Relay G-2 locksitself up over the following circuit: free pole of battery, relay G2,conductor conductor 229, front contact and armature 230, of relay G-2,conductor 225i, conductor 227- to ground at the inner left hand armatureof relay B2. Relay G2 connects the talking conductors of Fig. 2 throughto the talking conductors of Fig. l whereupon. the trunk and toll relayBl3 operates in series with the relay A5, Fig. 5, and lights thesupervisory lamp 100 as a ringing signal to the toll operator. Relay G2,Fig. 2, cuts off the bridge including relays C-2 and A-2. The operatornow operates her ringing key BK which impresses alternating current uponthe talking conductors and operates the alternating current relay Clwhich in attracting its armature operates the relay E-L This relay inattracting its right armature opens the cir- V cuit heretofore traced,which has been holding relay F6, Fig. 6, energized. This relay inretracting its armature 68? connects ringing current to the called linethrough the upper winding of relay F6. This ringing current isautomatically continued until the called party removes his receiver,resulting in the increase in the current through the upper winding ofrelay F6 causing the same to operafe removing the ringing current. Theattraction of the armature 635 of this relay closes a locking circuitfor the same over control conductor 600. The extension of the tip andring conductors by relay F-6 to the called line operates relay A4 overthe winding of which talking current is fed to the called line. RelayA-% in operating energizes relay B% which in attracting its right handarmature applies ground to the conductor 41 1- to hold up relay F6, Fig.6, independently of the relay El. Relay Bl in attracting its left handarmature opens the connection of battery through the windings of relayA5, Fig. 5, to the talking conductors 407, 408, leading back to theoperator's position which causes the deenergization of supervisory relayB l3. This relay in retracting its armature extinguishes the supervisorylamp Ill) 100 which notifies the operator that the subscriber hasresponded. Talking current is fed to the called line over the windingo-f relay r -4 and the repeating coil 406. This talking circuit is astandard repeating coil transmission circuit used in long distanceconnections. Talking current is fed to the calling line from the callingdistant exchange. During conversation the trunk leading from thelefthand windings of repeating coil 406 through the right hand windingof the repeating coil (not shown) at the distant oflice is dry, inaccordance with standard practice. The operator may now request thesubscriber at the substation shown in 6 to deposit the necessary coinsin the coin box which may be of the type shown in said Patent 1,043,219.These coins in passing through the box strike gongs whereby the operatoris informed of the denominations of the coins inserted. When she issatisfied that the proper coins have been deposited 'she picks up herplug P-10, Fig. 10, and after touching the tip of the plug to the tip ofthe jack and finding the same idle, she inserts it into the collect jackJ-10. The insertion of the plug P-10 closes a circuit for relays E-91and E-99 over the sleeves of the plug and jack, and relay E-9l thereuponoperates the signals 1002, and 1003 at the positions in which themultiples of this jack appear. Relay 13-99 in operating disconnects thebusy test circuit and connects the dial D-lO to the tip of the plug.Battery on the sleeve of the plug causes the multiples of the seizedtrunk to test busy at the other positions. The operator knowing thenumber of the trunk shown in Fig. 3 because of the designations on thejacks themselves or the designation strips associated with the iacks,now rotates her dial to set the automatic switch shown in Fig. 1.0 toconnect with the multiples of the used trunk which appear in thisswitch. The automatic switch of Fig. 10 and all apparatus shown at theright of the dotted line is located at the distant automatic oiiice:that is to say in the same office with the selector of Fig. 3. Theequipment shown at the left of the dotted line of Fig. 10 is located atthe toll office. The insertion of the plug P-10 energizes the impulserelay 14-10 over the following circuit: free pole of battery, resistance1050, impulse springs of the dial, armature and front contact of relayll99, tip of the plug P-10, tip of the jack J 10, conductor 1005,conductor 1006, upper normally closed contact of ofl normal switch 1007,conductor 1008, impulse relay A-10, conductor 1009, conductor 1010, ringof the jack il-10, ring of the plug P-10 to ground. The impulse relay inopcrating energizes the usual slow to release relay B-10. Relay B-10 inattracting its outer right armature closes a circuit for the upperwinding of relay H-lO. This winding of relay 1 1-10 when energized isnot sufficiently strong to cause the relay to opcrate but is sufficientto cause relay H-10 to operate when the current through the lowerwinding is in the right direction to aid the current in the upperwinding; lower winding of relay H-lO will not cause the operation of therelay H-lO, when the current flowing in the upper winding opposes thatflowing in the lower winding. The lower winding however is shunted whilethe switch shaft is in its normal position.

-Upon the return movement of the dial the impulses are transmitted tothe impulse relay A-lO. Upon each retraction of the armature of thisrelay an impulse is transmitted over the following circuit to thevertical magnet 1013 of the switch; ground, armatureand back contact ofrelay A-10, inner armature and front contact of relay 13-10, lowernormally closed contact of aif normal switch 1007, slow relay C-lO,vertical magnet 1013 to free pole of battery. The first step of theswitch operates the off normal switch 100? which removes the shortcircuit from around the lower winding of the relay iii-10, whereuponrelay H-lO operates and shifts the armature 1012 from its normalconnection with the refund source of 110 volts negative current toconnection with the collect source of 110 volts positive cur rent.

Upon the first vertical step the 0H normal switch 100'? operates and thesucceeding impulses then pass by way of contact 1015 and the armatureand front contact of slow relay (3-10. Upon the cessation of theimpulses the slow relay C-10 releases preparing a circuit for the rotarymagnet 1016 closed upon the return of the dial for the units impulses.The impulses now pass from the back contact to the stepping relay A-10,inner armature and front contact of relay 3-10, contact 1015, armatureand back of relay 6-10, slow relay E-10, outer right hand armature andback contact of relay D-10, rotary magnet 1016 to free pole of battery.Relay E-10 in attracting its outer left armature energizes relay D-10which in attracting its left armature locks up to the outer rightarmature of relay 13-10. Relay E-10 in attracting its inner leftarmature operates relay F-lO. Relay 13-10 in attracting its rightarmature connects the rotary magnet in the stepping circuitindependently of the outer right armature of the relay D-10. Now whenthe units impulses have all been transmitted the slow relay E-lO, aftera slight interval, releases. The retraction of its inner left armatureopens the circuit through the left winding of relay F-lO. If at thistime the interrupter-1017 is on a metallic segment relay F-10 will beheld up by its armature. lVhen the interrupter passes to the nextinsulating segment relay F'10 releases .and its armature connects relayG10 over the inner right armature and front contact of relay D10 to theinterrupting 1na- :chine 1017. It will be apparent that the re- :lay F10is provided to insure that the first impulse to relay G10 will be a fullone.

The brushes 1018 and 1019, being now in contact with multiples 1020 and1021 of the trunk shown in Fig. 3, upon the first engagement of theinterrupting machine brushes with the metallic segment after relay Flhas released, an hnpulse is transmitted to the relay -G10 which, inattracting its armature connects the source of collect current by way ofthe brush 1018, multiple 1020, conductor 345, Fig. 3, uppermost armatureand front contact of relay D3, Fig. 3, conductor 3'37, brush 338,multiple 339, conductor 482, relay G4l, resistance 434C to ground. RelayGl connects relay K-d to the interrupter 1017 which is the same machineas that indicated by the same reference character in Fig. 10. Each timerelay K4 operates, it extends the conductor 432 to the ring conductor416 and tip conductor and thence to the called line, this circuitincluding switch hook springs of the substation telephone set, contact638 in the coin box, polarized magnet P of the coin box to ground.Current will flow through relay J-10, Fig. 10, to ground at the coin boxeach time relay G'-1'0 operates until the coins have been collected incase they are not collected upon the first operation of the polarizedmagnet P. When the polarized magnet P operates and collects the coinsthe contact 638 in the coin box at the substation is opened consequentlyrelay J1O no longer operates. Each time relay J1O operates tone isplaced on the toll switching trunk to indicate to the operator that theproper current is being sent out to the called line. This circuit leadsfrom a source 1022 over the front contact and armature 1023 of the relayH1-0, armature and front con tact of relay J"10, condenser 1-069, brush1019, multiple 1021, Figs. 10 and 3, which multiple is connected to thetip conductor of the trunk from whence it is transmitted to theoperators head set. The toll operator, ceasing to hear the toneimpulses, knows that the coins have been collected and pulls out theplug P10. If the polarized inagnet fails to collect the coins or if thecoin box fails to function properly for some reason or other the contact688 remains closed and the repeated impulses of tone will inform theoperator of this condition and she will pull out the plug and report theline. The removal of the plug causes the release of the impulse relayA-10 and slow relay E 10 which closes the following circuit for therelease magnet J1025; free pole of battery, magnet J1025, upper contactof the off normal s itch 1007, inner armature and back contact. of slowrelay B-10 armature and back contact of relay J lL-1O to ground. Therelease magnet restores the switch and the switch, upon reaching its110111121] position, restores oil nruimal switch, 100?.

it the operator had plugged into the refund jaeh R10, if for any reasonthe coins were to be rot-untied, the cun'ent in the lower winding ofrelay 1-1-10 would oppose that following in the upper winding and relayH- would not operate when the oil normal switch 1-00? opened the shuntabout the lower winding. Consequently the armatures of relay l-l10 wouldhave remained retracted, the armature 1012 connecting the refund sourceof negative on rent to the called line to operate the iola-r-ized ma netb P in the opposite direction to refund the coins to the subscriber.Armature 1023 at its contact would connect a source of refund tone 1027in circuit with the operators head set each time the relay J"-10operated. As

in the case where the coins were collected, the toll operator ceasing tohear refund tone impulses knows that the coins have passed through thebox and she removes the plug from the refund jack.

It is of course understood that the tone sources 1022 and 1027 are ofdifferent character for era nple, the refund source can he L pulsationsper second and the collect source 150 pulsations per second.

Assuming now that the desir d line when selected by the connector isbusy. In that condition the test multiple 626, Fig. 6, is grounded.lVhen test wiper 627 is set on the busy multiple 626, ground is extendedover brush 62?, conductor 628, contact 6 10 of relay ill-6, conductor 6%armature 6 12 and back contact ot relay H-6, conductor 6&3, relay (i-(ito free pole of: battery. Relay G 6 energizes and when relay E-(i reler"s locks itself up over the following circui tree pole of battery, relayG6, conuuctor 6&3, armature 642 and back contact of relay 1-1- 6,conductor Gil, make hefore break contact of relay ll6 right arniatureand front contact of relay G -6, eonductor 631, conductor 615 to groundat the armature (S16 and trout contact of relay l6. Relay (71-6 in thecase of a local call connects busy tone "from the source 045 to thecalling line. In the case a toll call this busy tone is not used, a thising signal being Yen to the operator instead. reason of the groundccnncctin to the mul: tiple 626 of the selected line i does not operate.(lonsequen't is not energized to open the c D Fig. as described the ca eof an line. nasinuch as 1' ll- .inains TI. lt ii" energized, relay F-d,whose circuit is main-

